FIG. 17 shows the configuration of a conventional light emitting module device. In a light emitting module device 100, light emitting modules 101 are arranged in a matrix, the light emitting modules 101 adjacent to each other are connected via connection points 102 for transmitting power, and a terminating apparatus 104 for a power line 103 is attached to the light emitting modules 101 at one end column. Each of the light emitting modules 101 has a control apparatus (not shown) which adjusts the light emission amount of the light emitting module 101 by itself. When the terminating apparatus 104 supplies power to the light emitting modules 101, power is sequentially transmitted to the light emitting modules 101, whereby all the light emitting modules 101 are supplied with power (see, for example, Patent Document 1). In the light emitting module device 100, the control apparatuses can control the light emission amounts of the respective light emitting modules 101. However, since the control apparatus is provided in each of the light emitting modules 101, the production cost increases.
FIG. 18 shows a light emitting module device configured so as to solve the above problems. A light emitting module device 200 includes a control box 202 which collectively controls the light emission amounts of a plurality of light emitting modules 201. Each of the light emitting modules 201 is configured such that the light emission amount thereof is adjusted in accordance with supplied power. Power lines 203 through which power is supplied extend from the control box 202 to the respective light emitting modules 201. The light emitting modules 201 are connected to the control box 202 via the power lines 203 by star topology. The control box 202 controls supply power to each of the light emitting modules 201, thereby controlling the light emission amount of each of the light emitting modules 201 (see, for example, Patent Document 2).
However, in star topology, since dedicated power lines 203 are individually used for connecting the control box 202 to the respective light emitting modules 201, the same number of pairs of lines as the number of the light emitting modules 201 are needed, and thus, the number of the lines is two times as many as the number of the light emitting modules 201. Therefore, the production cost can increase owing to the increase in the number of lines, and thus it has been desired that the production cost is reduced. In addition, it is also desired that the accuracy of signal communication to the light emitting modules 201 is improved.
Besides such light emitting module devices, there is known a plasma display that is capable of individually controlling the light emission amount of each portion of a plasma panel, and that uses a decreased number of power lines. FIG. 19 shows the plasma display. In a plasma display 300, a column power line group 302 and a row power line group 303 are arranged in a grid-like fashion in the plasma panel 301, and a rare gas is enclosed between the column power line group 302 and the row power line group 303. A column driver 304 and a row driver 305 apply a voltage only between a column power line and a row power line that are respectively selected, thereby causing the intersections of the power lines to emit light by discharge (see, for example, Patent Document 3 and Patent Document 4). In the plasma display 300, the column driver 304 and the row driver 305 individually adjust the discharge voltage at each light emitting portion, whereby the light emission amount at each light emitting portion is individually controlled. In addition, each power line is shared by a plurality of light emitting portions of the plasma panel 301, and therefore, the number of power lines that are needed decreased.
Then, it is conceivable to apply the configuration of the plasma display 300 to the light emitting module device, and replace the light emitting portions of the plasma panel 301 with the light emitting modules.
However, in such a light emitting module device, supply power to a plurality of light emitting modules flows in power lines, and as a result, the amount of the supply power flowing in the power lines increases. Therefore, if the supply power is sequentially changed for individually controlling the light emitting modules, increased radiation noise can be superimposed onto the supply power. Since each of the light emitting modules is controlled in accordance with the value of the supply power, the supply power can be regarded as a control signal for controlling the light emitting modules. The radiation noise is superimposed onto the control signal, and therefore, there is a possibility that the light emitting modules cannot be accurately controlled.
Patent Document 1 also discloses a light emitting module as shown in FIGS. 20(a) and 20(b), besides the above-described content. A light emitting module 400 includes: plural pairs of feed terminals 401; a control apparatus 402 which controls the light emission of the light emitting module 400; and plural pairs of communication terminals 403 connected to the control apparatus 402. The appearance of the light emitting module 400 in a plane view is rectangular. A pair of the feed terminals 401 and a pair of the communication terminals 403 are provided at each side of the light emitting module 400. A plurality of the light emitting module 400 are arranged so as to be adjacent to each other, whereby the feed terminals 401 and the communication terminals 403 of each light emitting module 400 are respectively connected to the feed terminals 401 and the communication terminals 403 of the adjacent light emitting module 400. By the connection between the feed terminals 401 of the adjacent light emitting module 400, power is supplied from each light emitting module 400 to the adjacent light emitting module 400. In addition, by the connection between the communication terminals 403 of the adjacent light emitting module 400, communication paths 404 are formed between the adjacent light emitting module 400. A control signal is transmitted or received between a plurality of the light emitting module 400 via the communication paths 404, whereby the plurality of light emitting module 400 operate in cooperation with each other.
However, in the light emitting module 400 described above, the control apparatus 402 of each light emitting module 400 needs to have a function of generating a control signal, and as a result, the cost increases. In addition, since a plurality of the light emitting module 400 are connected on a pair of the communication paths 404, it is necessary to provide IDs (identification codes) for identifying the individual light emitting module 400. As a result, the cost of a lighting apparatus increases because of a complicated providing method of the IDs.